Nope regular cantaloupes slip (turn loose from the vine) when ripe. exotics like charantais, some honeydews, most spanish melons, you have to judge by color change. As for the watermelon the actual stem stays green, the indicator is the tendral next to the stem. The old folks called it the the curl and Used "when the curl is dead as one indicator". It is not foolproof, some varieties like Sugar Baby, Black Diamond, Florida Giant seem to have the tendral dry prematurely.
Yes - this spring I planted the sugar baby variety. Harvested first one soon as tendril started getting brown. Oops, that WAS a little too early. Waited on next one a week after. It was a little too ripe but tasted great! Any more secrets?